Method of announcing low level of remaining liquid in dropper

ABSTRACT

This invention relates to a method of annoucing a low level of the remaining liquid in a dropper. According to the present invention, two electrodes are attached to the outer surface of a dropper, and a pulse of a stable level is applied to one of these electrodes. The remaining quantity of the liquid in the dropper can be detected automatically with ease by utilizing the variations of the electrostatic capacity occurring between these two electrodes. An annunciator is activated when it receives a signal representative of a low level of the liquid in the dropper, to inform a nurse of the necessity of replacing the dropper.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of announcing a low level of theremaining liquid in a dropper.

2. Description of the Prior Art

In a conventional method of this kind, a patient who is administered aliquid dropwise ascertains visually a low level of the remaining liquidin a dropper, and informs a nurse of this fact through a microphone,which is placed by the bed of the patient, shortly before the liquidruns out. The nurse who has receive this vocal information then renewsthe dropper.

According to this method, in which a patient visually ascertains a lowlevel of the remaining liquid in a dropper, he has to constantly careabout when the liquid will run out. This is a very heavy mental burdenon the patient, and compelling a patient to ascertain a low level ofsuch a remaining liquid is primarily very unreasonable. It is necessarythat this problem be solved as soon as possible so as to eliminate thepatient's mental burden.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method ofautomatically announcing a low level of the remaining liquid in adropper by attaching two elecrodes to the outer surface of the dropper,and applying a pulse to one of these electrodes to enable the remainingquantity of the liquid to be detected easily by utilizing the variationof the electrostatic capacity between the two electrodes, whereby theabove-mentioned unreasonable problem is solved.

The present invention, which has been developed with a view to solvingthe problems in a prior art method of this kind, is characterized inthat two detecting electrodes are attached to the outer surface of thelower portion of a liquid-containing dropper, to one of which detectingelectrodes a pulse of a stable level is applied, a difference between alevel of the pulse passed through the interior of the dropper when theliquid exists therein as an electrode and that of the pulse passedthrough the inverior of the dropper when the remaining quantity of theliquid in the dropper decreases to such an extent that the liquid doesnot work as an electrode, both of which levels are determined inaccordance with the electrostatic capacity between the two electrodes,being compared with a reference level, a judgement signal representativeof unfavorable results of this comparison actuating an annunciator.

The above and other objects as well as advantageous features of theinvention will become apparent from the following description of thepreferred embodiment taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation of a part of a dropper with detectingelectrodes attached thereto;

FIG. 2 is a block diagram of a circuit of a driving unit used when themethod according to the present invention is practiced;

FIGS. 3-6 are diagrams showing the principle of the operations accordingto the present invention;

FIG. 7 is a perspective view of another example of a detectingelectrode;

FIG. 8 is a perspective view of the detecting electrode of FIG. 7 whichis attached to a dropper;

FIG. 9 is a sectional view of terminal strips in the detecting electrodeof FIG. 7; and

FIG. 10 is a sectional view of an annular bore in the detectingelectrode of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, reference numeral 1 denotes a glass bottle or adropper consisting of a medially soft synthetic resin, which is hungfrom a suspender (not shown), with two detecting electrodes 2, 3 pastedon the lower portion of the dropper 1. Each of the detecting electrodes2, 3 is formed by bending aluminum foil suitably, this bent aluminumfoil being pasted on the dropper 1. A driving unit 4 shown in FIG. 2 isconnected to these detecting electrodes 2, 3.

In this driving unit 4, an AC pulse of a stable output level isgenerated by a high-frequency AC pulse oscillator 6 which receives thesupply of an electric current from a dC stabilizing power source 5, andthis pulse is guided via a detecting wire 7 such as a shielded wire,which is connected to one detecting electrode 2 via a conductive chip(not shown) attached to the detecting wire 7. The other detectingelectrode 3 is also connected to the input side of an amplifier circuitvia an identical detecting wire 7. A suitably amplified signal isdetected, and the level of this signal is compared with a referencelevel in a decision unit 9, a decision being made therein. The resultsof the decision is inputted to an operating circuit for an annunciator,which consists, for example, of a buzzer (not shown), through outputcircuits 10, 11.

FIG. 3 shows the condition in which a liquid exists between thedetecting electrodes 2, 3. A case where an AC pulse having a stablelevel is applied to the detecting electrode 2 will now be discussed.When the dropper 1 consists of an electrically insulating material, itworks as a dielectric. According, the pulse thus applied to thedetecting electrode 2 passes through the dropper 1 and is transmitted tothe liquid therein.

When the liquid is electrically conductive, it works as an electrode,and the pulse is transmitted to the opposite side of the dropper andthen to the detecting electrodes 2, 3 through the dropper again.

The quantity of energy of the pulse thus transmitted to the detectingelectrodes 2, 3 is determined in accordance with the electrostaticcapacity formed between the detecting electrodes 2, 3, and theelectrostatic capacity varies in proportion to the opposed areas of theelectrodes and in inverse proportion to the distance therebetween.Therefore, the quantity of energy of the pulse transmitted to theelectrodes 2, 3 in the condition shown in FIG. 3, in which the liquid isinterposed as an electrode between the electrodes 2, 3, is larger thanthat of the energy of the pulse transmitted to the electrodes 2, 3 inthe condition shown in FIG. 4, in which the liquid is no longerinterposed as an electrode between the same electrodes 2, 3.Consequently, the levels of the pulses passing between the electrodes 2,3 in these two cases differ in amplitude as shown by L₁, L₂ in FIGS. 3and 4.

Therefore, if the reference level in the level decision unit 9 is setbetween these levels L₁, L₂, the presence and absence of the liquid inthe dropper can be determined.

In the dropper shown in FIGS. 3 and 4, the detecting electrodes 2, 3 areprovided in a laterally opposed state. Even when the detectingelectrodes 2, 3 are provided in a vertically spaced manner as shown inFIG. 5, they are, of course, operated in the same way.

Also, even when, for example, an air introducing needle K, which isthrusted into a dropper 1 as shown in FIG. 6, is used as an electrodeinstead of the detecting electrode 2 or 3, the electrodes are, ofcourse, operated in the same way as mentioned above, though the pathalong which the pulse passes is shortened.

FIG. 7 onward show a modified example of the detecting electrodes. Sincethe previously-described detecting electrodes 2, 3 are formed out ofaluminum foil, they require a troublesome operation every time they areput to use, i.e., they have to be bent to obtain projecting electrodes.The example showing in FIGS. 7-10 consists of clip type detectingelectrodes which can simply be attached to a dropper 1 in a clampedstate. These detecting electrodes are employed only when the dropper 1consists of a bag of a medially soft synthetic resin. The constructionof these detecting electrodes will now be described.

These detecting electrodes consist of a pair of openable bars 13 of asynthetic resin having a hinge 12 at the joint ends thereof and adaptedto be opened and closed via the fulcrum hinge 12, semicylindricalrecesses 14 formed in an opposed state in the closing surfaces of theopenable bars 13 so that two annular bores are formed when theseopenable bars 13 are closed on a dropper 1, projecting clamp portions 16which are provided with metallic terminal plates 15 adapted to beopposed to each other when the openable bars 13 are closed, and whichare formed between the recesses 14, bolts 17 one end portion of each ofwhich is fixed to the relative terminal plate 15, and the other endportion of each of which is passed through the relative clamp portion 16and exposed to the outside, washers 18 which have detecting wires 7fixed thereto, and which are fitted over the outer end portions of thebolts 17, and nuts 19 screwed on the bolts 17 so as to fix the washers18 in a pressed state to the outer surfaces of the clamp portions 16.

Reference numeral 20 denotes a flexible latch formed by extending thefree end portion of one openable bar 13 and used to maintain the bars 13is a firmly closed state, and a cut 21 in which this latch 20 isinserted in a locked state is provided in the free end portion of theother openable bar 13.

In order to attach the detecting electrodes thus constructed to adropper (bag) 1, the two openable bars 13 are opened via the fulcrumhinge 12 as shown in FIG. 7, and a lower edge portion 1a of the dropper1 is inserted between the clamp portions 16 with the left and rightliquid discharge tubes 1b, which are provided on the dropper 1, insertedin the recesses 14. The bars 13 are then closed as shown in FIG. 8, sothat the lower edge portion 1a of the dropper 1 is pressed from bothsides thereof by the clamp portions 16. Consequently, the detectingelectrodes are combined unitarily with the dropper 1. When the loweredge portion 1a is pressed by the clamp portions 16, the terminal plates15 are also pressed in an opposed state against both side surfaces ofthe dropper 1. A pulse is applied to the electrode through the terminalplates 16 to detect the presence and absence of a liquid on the basis ofthe operational principle referred to above.

According to the present invention described above, a low level of theremaining liquid in the dropper is detecting automatically, and theannunciator is actuated by a signal representative of this informationon the liquid to inform a nurse of the necessity of replacing thedropper. Especially, the structure used to practice the method accordingto the present invention has advantageous features that it is capable ofdetecting the remaining quantity of the liquid in the dropper easily andreliably by utilizing the variation of the electrostatic capacity, whichoccurs between the two electrodes on the dropper when a pulse is appliedto one of the electrodes.

The present invention is not, of course, limited to the aboveembodiment; it may be modified in various ways within the scope of theappended claim.

What is claimed is:
 1. A method of announcing a low level of theremaining liquid in a dropper, comprising the steps of:applying a pulseof a stable level to at least one of detecting electrodes attached to anouter surface of a lower portion of a liquid-containing dropper;comparing a level of said pulse passed through an interior of saiddropper with a reference pulse level, said reference pulse level beingbetween a level of said pulse passed through said interior of saiddropper when said liquid exists therein for defining an electrostaticcapacity between said detecting electrodes and that of said pulse passedthrough said interior of said dropper when a remaining quantity of saidliquid in said dropper decreases to such an extent that a significantlyreduced electrostatic capacity is defined between said detectingelectrodes; and automatically actuating an annunciator when a judgementsignal representative of unfavorable results derived from said step ofcomparing with said reference pulse level.
 2. The method of announcing alow level of the remaining liquid in a dropper as in claim 1, whereinsaid step of applying a pulse of a stable level includes the steps ofapplying a certain level of pulses to an electrode, and obtaining alevel of pulses at another electrodes, and wherein said step ofcomparing with said reference pulse level includes the step of comparingsaid level of pulses at said another electrode with said reference pulselevel.